1. Technical Field
This invention relates to electrical connectors and, more particularly, for a fixture used to interconnect coaxial cable connectors to stripline circuits.
2. Discussion
The present invention finds particular utility for transmitting high frequency signals, in particular signals having frequencies of 3 GHz and above. This range is often referred to generally as the microwave frequency range. It is well known that special precautions must be taken when dealing with signal transmission circuits in this frequency range. Otherwise unwanted transmission losses, reflections and other undesirable characteristics can result.
Microwave signals are often carried on shielded coaxial cables. These cables are typically used to transmit microwave signals to and from various end devices. Many of these end devices require that connections to them are made by way of flat or "stripline" conductors residing on a surface of a dielectric board (hereinafte "a stripline circuit"). Examples of such devices include power splitters, mixers, hybrid couplers, directional couplers, filters, attenuators, phase shifters, antenna elements and antenna arrays.
The stripline conductors are sandwiched between two ground planes. The purpose of the ground planes is to provide the outer grounding surfaces above and below the center conductor in the same way that the outer conductor of a coaxial transmission line surrounds the center conductor. Stripline may be thought of as a flattened form of coaxial cable. Since the electrical fields around the center conductor only extend a short distance to either side, conductors are not required to the sides of a stripline circuit. In some applications it is desirablle to reduce the ground plane spacing as much as possible because space limitations may require the use of smaller circuits.
Female coaxial connectors such as SMA, standing for Sub-Miniature Series A (military designation) connectors, are often used to couple the coaxial cable to the stripline conductors. SMA connectors are well known in the art and they generally include a center pin having a tab on its inner end and a female recess on its opposite end. The center pin is surrounded by a Teflon insulator which serves to support the center pin in the outer housing. The housing acts as the outer coaxial conductor around the center pin.
It is fairly easy to make high quality transitions between SMA connectors and stripline circuits when the ground plane spacing of the stripline circuit and diameter of outer conductor of the SMA connector are essentially the same. However, when the stripline circuit ground plane spacing decreases below about 0.060 inch that certain heretofore unresolved problems result. These problems include providing electrical and mechanical connections between the connector housing and the stripline ground planes, as well as between the connector center pin tab and the stripline conductor. Other problems include compensating for the large electrical discontinuities created by the dimensional differences.
The present invention is directed to solving one or more of these problems.